The other day, I wrote about rats at the behest of a reader and member of a small writing club of which I am a part. Below is her response to the rat post:

. . . I contest: “Commensalism is a relationship between two species where one of the species benefits and the other species is not affected. Rats often live with or near humans. They are not parasites. They are commensals.”

I AM VERY AFFECTED BY THE RATS.

Another member of the writing club commented:

I, too, have seen a rat in a toilet, and have not been the same since. Thought, it was small, so maybe a mouse?

The bit about the lab rats reminded me about an interesting fact I picked up from my time working with lab animals. Sacrificing non-human primates which is the actual scientific term for when your experiment is done and you need to harvest whatever organ you are studying, is a gruesome physically challenging act relative to the size of the animal. But rats are “sac”-ed in little rat guillotines!

Meanwhile, the third member of the writing club stuck up for rats:

I have some affection for the scrappy subway rats, especially the one running off with a whole slice of pizza! I also love the movie Ratatouille. So, I couldn’t help myself and I Googled rat guillotine. HIGHLY DISTURBING. I don’t recommend.

Later on in the email chain, the third member reiterated her recommendation:

. . . [s]eriously, don’t Google rat guillotine.

I think she really meant to say:

Please, please Google rat guillotine.

Sacrificing non-human primates, sac-ing lab rats with little rat guillotines, just the stuff of writing. While I did not Google rat guillotine, I did go down the rabbit hole yesterday with ecological associations and their fuzzy borders. I tried too hard to understand the distinction between commensalism and parasitism. It took me to the unintended harvest of the fact that viruses are the most abundant biological entity on earth, with which I could do so much. I also now know more about human head and body lice than is probably good for me to know, given my history. Head lice feed on discarded scalp skin while body lice actually puncture the skin and suck the blood. Some say that head lice are commensals while body lice are ectoparasites, but there is not agreement.

The rabbit hole did lead me, this time, to the very specific answer sought. Apparently, scientists agree that humans are affected by rats though the borders of that are still not entirely clear.

Since the word commensal implies no damage to the host these rodents [brown rats, house mice, roof rats] might more precisely be termed kleptoparasitic.

– Researchers D. McDonald and M. Fenn

Kleptoparasites steal the food of their host. Let us not forget, that rats are also vectors for and direct zoonotic carriers.

Another researcher suggested rats as synanthropes. A synanthrope is a member of a species of “wild animals or plants that live near and benefit from an association with humans and the . . . habitats humans create around them (houses, gardens, farms, roadsides, garbage dumps).” A synanthropic species “includes a large number of what humans regard as pest species.” A pest is a “plant or animal detrimental to humans or human concern,” with rats causing the detriment of “infestation.” Infestation means to be overrun by pests or parasites. A very quick look at the Orkin site puts it more in perspective. Rats steal our food. In the process of stealing our food, they can contaminate it with their rat stuff and carry disease into human habitats. And, they multiply quickly.

Enough said. I remain enamored of the word commensal, but rats are synanthropes. They are kleptoparasites. They are pests. They are vectors and direct zoonotic carriers.

The featured image is totally unrelated. It’s meant to take your mind off the rats. This was seen in Georgetown this evening. There were more. It was a gang like the Penguin’s in Batman Returns.